Exploiting the Cationic Size Effect to Improve the Curie Temperature of Hybrid Perovskites Photoferroelectric Semiconductors

Ferroelectric materials with Curie temperature (Tc) below room temperature severely limit their practical applications. Although research on hybrid perovskite photoferroelectrics is ongoing, effective regulation of Tc still poses significant challenges. Herein, we utilized the cationic size effect to successfully regulate the Tc of hybrid perovskite photoferroelectric semiconductors. As the perovskitizer was replaced by a smaller-sized MA+ (methylammonium) with a larger-sized EA+ (ethylammonium), not only was the ferroelectricity of the hybrid perovskite well maintained but the Tc of (PA)2(MA)2Pb3Br10 (315 K) to (PA)2(EA)2Pb3Br10 (385 K) (PA is n-propylaminium) increased by 70 K, which was mainly due to the significant increase in the energy barriers that the system needed to overcome during the phase transition. Subsequently, we achieved efficient self-powered X-ray detection through the ferroelectric-induced bulk photovoltaic effect (BPVE) in (PA)2(EA)2Pb3Br10. The devices based on (PA)2(EA)2Pb3Br10 single crystals exhibit an outstanding sensitivity of 95 μC Gy–1 cm–2 and a low detection limit of 239 nGy s–1 at 0 V bias under X-ray radiation. This study provides an effective approach for designing and constructing high-temperature multilayer photoferroelectric semiconductors in the future.